refactor 'dir = ' into 'set_dir()'

This should have little/no gameplay effect right now, just paving the
 way for directional lights.
Replaced handle_rotation() on buckly things with this.

Signed-off-by: Mloc-Argent <colmohici@gmail.com>

code/modules/shieldgen/emergency_shield.dm

@@ -13,7 +13,7 @@
 	var/shield_idle_power = 1500		//how much power we use when just being sustained.
 
 /obj/machinery/shield/New()
-	src.dir = pick(1,2,3,4)
+	src.set_dir(pick(1,2,3,4))
 	..()
 	update_nearby_tiles(need_rebuild=1)
 

code/modules/shieldgen/sheldwallgen.dm

@@ -154,7 +154,7 @@
 		T2 = T
 		var/obj/machinery/shieldwall/CF = new/obj/machinery/shieldwall/(src, G) //(ref to this gen, ref to connected gen)
 		CF.loc = T
-		CF.dir = field_dir
+		CF.set_dir(field_dir)
 
 
 /obj/machinery/shieldwallgen/attackby(obj/item/W, mob/user)

code/modules/shieldgen/shield_capacitor.dm

@@ -149,5 +149,5 @@
 	if (src.anchored)
 		usr << "It is fastened to the floor!"
 		return
-	src.dir = turn(src.dir, 270)
+	src.set_dir(turn(src.dir, 270))
 	return